1. Field
The following description relates generally to wireless communications, and more particularly to generating and transmitting reference signals.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), evolution data optimized (EV-DO), etc.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple mobile devices. Each mobile device may communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in peer-to-peer wireless network configurations.
Moreover, for example, devices can transmit demodulation reference signals (DM-RS) to the base stations to assist in demodulating communications from the devices. In some wireless communication systems, such as LTE release 8, orthogonality (or at least pseudo-orthogonality) of DM-RSs related to disparate devices can be implemented by transmitting the DM-RSs according to different shifts of a sequence of resource elements. The shift can be defined at least in part according to an identifier specific to a cell of the base station with which the device communicates. Moreover, the sequence can also be initialized according to the identifier of the cell. Furthermore, in an example, a wireless communication system can support uplink multi-user MIMO where multiple cells (and/or base stations) can schedule joint uplink resources to the device. Thus, the device can simultaneously communicate with the base stations over the jointly scheduled uplink resources (e.g., to increase uplink bandwidth in the wireless communication system).